The present invention relates generally to a drill guide for drilling a hole at an oblique angle through two adjacent surfaces of a nut having a threaded interior. The present invention further relates to method for drilling holes, especially lockwire holes, using the drill guide where the nut to be drilled is already fastened to the workpiece or otherwise is inaccessible to conventional machine tools, such as a drill press.
Lockwires have often been used with threaded fasteners to prevent their inadvertent rotation and unthreading. These threaded fasteners are typically in the form of or have a hexagonally shaped nut (hereinafter referred to interchangeably as xe2x80x9chexagonal nutsxe2x80x9d or xe2x80x9chex nutsxe2x80x9d). One example of such nuts is a coupling nut commonly referred to as a B-nut. The B-nut is used to provide a leak proof connection for a fluid-conducting tube and a projecting nozzle (of the fitting) that the tube end is pressed over. The B-nut is usually threaded down over the tube end and onto the fitting past the nozzle to provide a seal. The lockwire fixes the B-nut relative to the fitting so that the B-nut does not rotate and unthread due to external forces, such as vibration. The fitting or mate to the B-nut can also be lockwired.
Typically, the lockwire is passed through a transverse hole in at least two threaded fasteners and is twisted back on itself in alternating clockwise and counterclockwise directions between the threaded fasteners. The process is then duplicated between additional threaded fasteners until the entire threaded fastener pattern has been safety wired. Following the required stringing and twisting, the wire is cut and bent into a certain position. (In the case of the B-nut, the lockwire is typically passed through holes formed in the B-nut and secured to a boss on the base or to the mating fitting.)
For hexagonal nuts, the hole (or holes) for the lockwire is typically formed by drilling through one or more of the outer nut lobes or corners. In the past, the drilling of a lock wire hole in such nuts has been an awkward and time-consuming task. The lockwire hole in the nut lobe or corner is typically drilled at a 30xc2x0 angle relative to the face of the nut (i.e., is an oblique angle). This sharp oblique angle often results in drilling problems because the angle of the nut face tends to divert the line of action of the drill, often resulting in broken drills, a damaged drill part or an imperfect hole through the nut lobe or corner. These and other difficulties have led others to seek alternatives to the use of lockwires for such nuts. See, for example, U.S. Pat. No. 5,362,111 (Harbin), issued Nov. 8, 1994 (spring clip used to prevent rotation of coupling nuts); U.S. Pat. No. 5,094,491 (Berghammer et al), issued Mar. 10, 1992 (integral locking mechanism used to prevent rotation of coupling nuts).
U.S. Pat. No. 5,409,327 (Schroeder), issued Apr. 25, 1995, discloses an apparatus for drilling lockwire holes in lockwire nuts. This apparatus includes a variable speed drill press mounted on a work bench that has a vertically movable drill quill supporting a rotating drill spindle on one end of which is mounted a drill chuck for holding and driving a drill bit for drilling a hole in the lockwire nuts. An N/C microprocessor is also coupled to the drill press for controlling the vertical motion of the drill quill. The nut holder of this apparatus includes a collet chuck having three jaw inserts, each of the jaw inserts having a drill guide that guides the drill bit at the appropriate angle against the faces of the nut to drill lockwire holes through the nut.
The apparatus of the Schroeder patent is undoubtedly useful for precise drilling of lockwire holes in hexagonal nuts in a machine shop or when the nuts are not currently fastened to the workpiece. However, in some instances, lockwire holes may not have been drilled in the hexagonal nut before it is fastened to the workpiece or need to be drilled in the nut at a location remote from the machine shop. In particular, if lockwire holes need to be formed in nuts fastened to the workpiece, it may not be possible (or desirable) to unfasten the nut to drill the needed lockwire hole(s). Unfortunately, the apparatus of the Schroeder patent probably cannot be easily used to form lockwire holes in hexagonally shaped nuts that are already fastened to the workpiece.
Accordingly, it would be desirable to provide a device that will allow the precise and relatively easy drilling of lockwire holes in hexagonal nuts and other nuts requiring lockwire holes. In particular, it would be desirable to be able to easily and precisely drill such lockwire holes while the nut(s) still fastened to the workpiece or when the lockwire holes need to be formed in the nut at a location remote from a machine shop.
The present invention relates to a drill guide that is capable of guiding the drilling of holes, in particular lockwire holes, transversely through one lobe or corner of a nut at an oblique angle to a face of the nut. The drill guide comprises at least one guide component having:
(a) a first side and a second side transverse to the first side;
(b) the first side having a recess with first and second surfaces for receiving the corner of the nut, the first surface being closer to the second side;
(c) a drill bit guide for guiding a drill bit of a drill, the drill bit guide being accessible from the second side and extending towards the first surface of the recess along a longitudinal axis in the direction of the second surface of the recess so that the drill bit is capable of drilling a hole transversely through the corner of the nut at an oblique angle relative to the face of the nut that the drill bit initially engages.
The present invention further relates to a method for drilling holes in such a nut that is already fastened to the workpiece. This method comprises the steps of:
(a) providing the drill guide comprising the at least one guide component;
(b) positioning the at least one guide component of the drill guide so that the one corner of the nut is securely received by the recess;
(c) inserting the drill bit of the drill into the drill bit guide so that the drill bit engages a face of the nut closest to the first surface of the recess;
(d) drilling a hole transversely through the corner of the nut at an oblique angle relative to the face of the nut that the drill bit initially engages.
The drill guide and method of the present invention allows holes, in particular lockwire holes, to be easily and precisely drilled transversely through a corner of the nut, even though the angle being drilled is oblique relative to the face of the nut that the drill initially engages. Moreover, the drill guide of the present invention allows such holes to be easily and precisely drilled transversely through the corner of the nut, even when the nut is already fastened to the workpiece and is not easy (or desirable) to unfasten the nut. An alternative embodiment of the drill guide of the present invention also allows the guide component to be disassembled in the event the drill bit is broken so that the broken bit can be easily removed from the guide component. Another alternative embodiment of present invention also allows for replacement of drill bit guide that typically contains a bore for guiding the drill bit in the event the bore becomes damaged, clogged or to permit easier removal of a broken drill bit. Yet another alternative embodiment of the present invention comprises two such guide components that can be releasably joined together to allow easy and precise drilling of such holes at opposite corners or lobes the nut, in particular, a hexagonal nut.